One big advantage of the P-38L is it's ords carrying. I use a thrustmaster cougar panel and the TARGET software to set salvo buttons so just by pushing a button I get the desired salvo. Very useful. They come in two packs but one will do. Split a pack with a friend and the price is not bad.
As FLS noted, elevator trim, is nice feature. Once you get used to manual elevator trim you will not want to go back to the stiffness of auto trim.
Two stage firing trigger is good for the 38 and other canon planes. Pull the trigger halfway to use just the 50s, then full pull for the canon and 50s.
The cougar panel has press to hold, spring loaded rocker switches with a neutral center that is super for RPM setting which is very helpful for the 38 to save fuel. Use E6B settings.
Make sure you have WEP easy to access.